CHAPTER XXI MILES AND GRINNELL GLACIERS
LOCATION AND RELATIONSHIPS
The Miles and Grinnell Glaciers are located just north of Childs Glacier, 25 or 30 miles above the mouth of Copper River (PL XCIQ), in the lower part of the canyon by which the river crosses the Chugach Mountains. At this point the Copper River valley is from 2-J to 4 miles wide at the bottom and its walls rise abruptly to elevations of from 3000 to 6000 feet. Farther south the valley walls flare apart, the width being 18 miles near the sea; and the glaciers discussed in this chapter are at the head of the V-shaped indentation with which the Copper River canyon ends.
Here four glaciers enter the valley near by at right angles to its course (Map 9, in pocket), Miles Glacier coming from the east and Childs, Grinnell, and Allen Glaciers from the west. Their termini are from 125 to 200 feet above sea level. Miles and Allen Glaciers extend completely across the main valley, forcing the Copper River first against one mountain wall, then the other, so that it writhes between the glaciers in a sinuous course. Miles and Allen Glaciers, like Childs Glacier, each act as a dam to the river, causing rapids opposite the end of each of the three glaciers, and above these, such relatively slack water as to give rise in each case to a lake-like expanse. The expansion above Childs Glacier is a broad lake, into which Miles Glacier discharges icebergs, but the other expansions are mere enlargements of the width of the river. There is no name for the rapids opposite the end of Childs Glacier, but the rapids opposite the termini of Miles and Allen Glaciers are called Abercrombie Rapids and Baird Canyon Rapids respectively.
Copper River is fed chiefly by glacial streams, receiving the drainage of some of the glaciers on the southern side of the Alaska Range, of a large proportion of the glacier system of the Wrangell Mountains, and of the glaciers along 200 miles of the northern slopes of the Chugach Mountains. To this already great supply is added much water from Allen, Miles, and Childs Glaciers.
After the railway crosses the river by the high s.teel bridge between Miles and Childs Glaciers it passes over the tip of Grinnell Glacier, and close to the northern part of Miles Glacier near Abercrombie Rapids.
General Description. Miles Glacier (PI. XCDJ) flows westward into the Copper River valley from an unexplored source in the Chugach Mountains. Only the lower 15 miles of the glacier have been mapped (Map 9), but much more than this is visible from the railway, and it is probably 40 or 50 miles long.1 It rises in snowfields, north of Bering and Martin River Glaciers, where Mt. Hawkins * and several other peaks rise
i Named in 1910 for the late E. C. Hawkins, the engineer who built the Copper River and Northwestero Railway.